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1.
Potassium Release Kinetics and Water Retention of Controlled-Release Fertilizers Based on Chitosan Hydrogels 总被引:2,自引:0,他引:2
Controlled release fertilizer (CRF) hydrogels were prepared from poly(vinyl alcohol), poly(vinyl alcohol)/chitosan and chitosan
using glutaraldehyde as a crosslinker. Intermolecular interactions of the CRF hydrogels were elucidated using FTIR. Water
absorbency characteristics of the CRF hydrogels were also studied. It was found that the CRF hydrogels exhibited the equilibrium
swelling ratio (SR) in the range 70–300%. The water retention of soil containing the CRF hydrogels was also examined. It was
found that the CRF hydrogels increased the water retention of the soil. After 30 days, soil containing the PVA-, PVA/CS- and
CS-hydrogels showed the water retention capacities of 25%, 10% and 4%, respectively. While the soil without the CRF hydrogel
had already given off most of the water. The release behavior of potassium from the CRF hydrogels, both in deionized water
and in soil, was investigated. In soil, the potassium release mechanism from the PVA- and PVA/CS-hydrogels were non-Fickian
diffusion. On the other hand, the CS hydrogel showed, n value that was close to 1.0 corresponding to case II transport. In deionized water, all the CRF hydrogels showed small values
of release exponent (n < 0.5) indicating a quasi-Fickian diffusion mechanism. 相似文献
2.
The SO4–S and NO3–N concentrations and pH in bulk precipitation, throughfall, stemflow and soil water for the 1994–2004 period were studied
in pine forests in Latvia (Rucava and Taurene Integrated Monitoring stations). The SO4–S and NO3–N concentrations decreased over the study period, simultaneously with a decrease of acidity in precipitation. The changes
were more evident in the western part of Latvia, probably due to declining long-range air pollution from West Europe. The
trend of decreasing sulphate concentrations and increasing pH in precipitation were not followed by respective changes in
soil water. In the upper soil horizon sulphate ion concentrations and acidity increased in soil water. Over the observation
period, nitrate concentrations also showed an increasing trend in soil water at Rucava and Taurene, but these changes were
not statistically significant. 相似文献
3.
Lomesh Dutta H. Eric Nuttall Al Cunningham Garth James Randy Hiebert 《补救:环境净化治理成本、技术与工艺杂志》2005,15(4):101-111
A new use for biofilm barriers was developed and successfully applied to treat nitrate‐contaminated groundwater down to drinking water standards. The barrier was created by stimulating indigenous bacteria with injections of molasses as the carbon donor and a combination of yeast extract and trimetaphosphate as nutrients. This injection of amendments results in bacterial growth in the aquifer, which attaches to the sand grains to create a reactive semipermeable biofilm. The biofilm barrier presented in this article reduced the migration of contaminants and provided an active zone for remediation. The cylindrical biobarrier was constructed using eight wells on the perimeter forming a 60‐foot‐diameter reactive biodenitrification region. Another well at the center was installed to continuously extract the treated water. The intent was to produce a continuous source of nitrate‐free water. The system operated for over one year, and during this period, the biobarrier was revived multiple times by reinjecting molasses in the perimeter wells. Nitrate concentrations of treated water decreased from 275 mg/L (as nitrogen) to < 1 mg/L. © 2005 Wiley Periodicals, Inc. 相似文献
4.
In Japan, melting-furnace fly ash (MFA) generated from ash melting and gasification/melting plants is considered an “urban
mine” due to its high metal content. This study aimed to develop a novel approach to pretreating MFA for metal recovery. Water
extraction with CO2 bubbling was investigated because MFA mainly consists of water-soluble salts containing elements such as Cl, Ca, Na, and
K. Instead of acid addition, CO2 bubbling was applied to maintain the optimal pH for minimizing the release of target metal elements and maximizing the removal
of undesirable elements during water extraction. The results revealed that CO2 bubbling effectively decreased the release of Pb, Zn, and Cd into the treatment water. This was mainly due to coprecipitation
with CaCO3, which was primarily formed by the reaction of Ca2+ from the MFA with CO3
2− from the CO2 gas. The bubbling process also helped accelerate the removal of Cl from MFA. Furthermore, the study showed that it is possible
to lower the water-to-solid ratio to 5 with only a slight reduction in water extraction effect. Finally, approximately four
times the concentration of target metals (rare metals and Cu, Pb, and Zn) was achieved by removing 90% of Cl, 70%–90% of Na
and K, and 30%–40% of Ca through water extraction with CO2 bubbling, resulting in a concentration of target metals that was nearly equal to that of ore. 相似文献
5.
Izumi Noguchi Kentaro Hayashi Masahide Aikawa Tsuyoshi Ohizumi Yukiya Minami Moritsugu Kitamura Akira Takahashi Hiroshi Tanimoto Kazuhide Matsuda Hiroshi Hara 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):67-75
Temporal trends of non-sea salt (nss-) sulfate and nitrate were analyzed from nationwide precipitation chemistry measurements
provided by the Ministry of the Environment (MOE) for the 1988–2002 fiscal years (April–March). The concentrations and deposition
of nss-sulfate were found to be decreasing, and those of nitrate were stable or slightly increasing at most sites. These deposition
trends were discussed from the viewpoint of emissions of SO2 and NOX during the period of interest. Because monitoring techniques have changed in the number of active sites, samplers, and analytical
methods during the operation period, the median of all annual depositions measured in Japan in a specific year was selected
as the annual representative. The contribution of specific emission sources was also calculated for 1990 on the basis of the
nss-sulfate and nitrate deposition in Japan obtained with a model simulation in which the model did not include volcanic emissions
from Mt. Oyama, Miyakejima Island, which began to erupt suddenly and violently in 2000. For nss-sulfate, the calculated deposition
agrees well with the intensity and trends of the median up to 1999. After 2000, a higher deposition than calculated in the
preceding years was evident, which is attributable to the volcanic SO2 from Mt. Oyama. For nitrate, both the calculated and observed depositions were slightly increasing; however, the calculation
was found to exceed the observation. 相似文献
6.
Eduardo Lopes Cancellier Fien Degryse Douglas Ramos Guelfi Silva Rodrigo Coqui da Silva Mike John McLaughlin 《Journal of Polymers and the Environment》2018,26(12):4388-4395
Methods to determine nutrient release rates of coated fertilizers usually rely on chemical analyses, which often are time-consuming and/or expensive. Our goal was to develop an innovative and rapid low-cost method to evaluate nutrient release from polymer coated MAP or urea using conductometry. The release in water is determined by measuring the electric conductivity (EC) over time, with intervals dependent on release rates. In the case of soluble salt fertilizers, EC can be immediately determined and converted to a concentration using a calibration curve. In the case of urea, an additional step is needed to convert the neutral urea into ammonium. The release rates in water were assessed for a range of commercial and laboratory-coated fertilizers. A validation test demonstrated strong agreement with the release determined using analytical techniques. The EC method hence offers an easy way to quickly evaluate the time course of release of nutrients from controlled-release fertilizers. 相似文献
7.
Tara Sankar Pathak Jung-Ho Yun Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2010,18(1):45-56
Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy.
Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in
various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared
to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size
distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium
alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around
200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation.
First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step
is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue
varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates.
Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered
as three consecutive first order reactions. 相似文献
8.
Shaodong Xie Yuanhang Zhang Li Qi Xiaoyan Tang 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):217-229
In the Beijing area, March and April have the highest frequency of sand-dust weather. Floating dust, blowing sand, and dust
storms, primarily from Mongolia, account for 71%, 20%, and 9% of sand-dust weather, respectively. Ambient air monitoring and
analysis of recent meteorological data from Beijing sand-dust storm periods revealed that PM10 mass concentrations during dust storm events remained at 1500 μg m−3, which is five to ten times higher than during non-dust storm periods, for fourteen hours on both April 6 and 25, 2000. During
the same period, the concentrations in urban areas were comparable to those in suburban areas, while the concentrations of
gaseous pollutants, such as SO2, NO
x
, NO2, and O3, remained at low levels, owing to strong winds. Furthermore, during sand-dust storm periods, aerosols were created that consisted
not only of many coarse particles, but also of a large quantity of fine particles. The PM2.5 concentration was approximately 230 μg m−3, accounting for 28% of the total PM10 mass concentration. Crustal elements accounted for 60–70% of the chemical composition of PM2.5, and sulfate and nitrate for much less, unlike the chemical composition of PM2.5 on pollution days, which was primarily composed of sulfates, nitrates, and organic material. Although the very large particle
specific surface area provided by dust storms would normally be conducive to heterogeneous reactions, the conversion rate
from SO2 to SO4
2− was very low, because the relative humidity, less than 30%, was not high enough. 相似文献
9.
Hydrogeomorphological Controls on Groundwater Quality in the Rattaphum Catchment (Songkhla Lake Basin), Thailand 总被引:1,自引:0,他引:1
N. Panapitukkul A. Pengnoo C. Siriwong W. Chatupote 《Water, Air, & Soil Pollution: Focus》2005,5(1-2):149-163
The Rattaphum Catchment comprises four major hydrogeomorphic units: mountains, footslopes, plains and inland swamps around
a lake system. The area accommodates three main agro-ecosystems: vegetable, rubber and fruits. During the high-rainfall period,
groundwater levels rise near to the soil surface in all agro-ecosystems. The high water levels remain for 3–4 months in the
coastal plain, while in other areas the groundwater level fluctuates according to the intensity of rainfall events during
the 2–3 months of the rainy season.
Groundwater salinity is higher near Songkhla Lake and decreases rapidly inland. It is generally lower near streams. Salinity
is also lower during periods of higher recharge, increasing slightly during the dry season due to leaching of chemicals from
the agricultural areas. In the saturated sandy soils with high hydraulic conductivity and in the vegetable agro-ecosystem
areas with high water levels, the NO3 level in groundwater always exceeds the WHO standard. Variations in NO3 levels are closely related to patterns of landuse, with higher nitrate levels commonly found in vegetable areas and lower
levels associated with fruit and rubber tree plantations. Nearly all groundwater and surface water is contaminated by coliform
bacteria, with the level of contamination controlled by groundwater levels, the amount of rainfall and farm activities. Vegetable
agro-ecosystems, which have the most intensive cropping system, were found to be the most polluted. In all of the agro-ecosystems,
the most polluted period coincided with the first series of rainfall events. 相似文献
10.
G. Q. Liu S. Y. Wang X. J. Zhu S. M. Liu J. Zhang 《Water, Air, & Soil Pollution: Focus》2007,7(6):593-605
The health of near shore marine ecosystems has long been a concern because of its importance to coastal areas. Jiaozhou Bay
(JZB) is one such marine ecosystem experiencing rapid water quality degradation in the last several decades. From the area
surrounding the bay, the nutrients discharged into the bay through surface water and groundwater has been greatly changed.
The thickness of the aquifers and the permeability is relatively high, the concentrations of nutrients in the groundwater
are generally high, and so the groundwater discharged into JZB is very significant. However, no attempt has ever been made
to evaluate the amount of nutrients discharged into the bay area via groundwater. In this study, the cross-section method
and water balance method were used to estimate the amount of groundwater and nutrients discharged into JZB via the subsurface.
Groundwater was monitored and sampled at aquifers surrounding the bay area, and some previously available data was also analyzed.
The results indicated that groundwater from the Baisha Aquifer east of JZB now is the major source of nutrients (nitrate,
dissolved SiO2) being discharged into the bay. The concentrations of nutrients in the groundwater have been increasing with intensive agricultural
land use. However, Dagu Aquifer, the largest aquifer north of JZB, only provides limited nutrients to the bay area because
of the construction of a low permeability subsurface dam. Historically, during the 1970s to the 1990s, the Baisha Aquifer
experienced seawater intrusion due to excessive groundwater withdrawal. The same was true for the Dagu Aquifer from the 1980s
to the 1990s. Because of this, no significant nutrients were discharged into the bay. 相似文献
11.
A. Matsuki Y. Iwasaka G.-Y. Shi H.-B. Chen K. Osada D. Zhang M. Kido Y. Inomata Y.-S. Kim D. Trochkine C. Nishita M. Yamada T. Nagatani M. Nagatani H. Nakata 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):101-132
This study focuses on providing a direct insight into the process by which sulfate is formed on mineral dust surface in the
actual atmosphere. Six sets of aerosol measurements were conducted in the outskirts of Beijing, China, in 2002–2003 using
a tethered balloon. The mineralogy of individual dust particles, as well as its influence on the S (sulfur) loadings was investigated
by SEM-EDX analysis of the directly collected particles.
The mixed layer in the urban atmosphere was found to be quite low (500–600m), often appearing as a particle dense stagnant
layer above the surface. It is suggested that mineral dust is a common and important fraction of the coarse particles in Beijing
(35–68%), and that it is relatively enriched with Calcite (>28%).
An exceptional amount of S was detected in the mineral particles, which can be explained neither by their original composition,
nor by coagulation processes between the submicron sulfates and the dust. Heterogeneous uptake of gaseous SO2, and its subsequent oxidation on dust was suggested as the main pathway that has actually taken place in the ambient environment.
The mineral class found with the largest number of particles containing S was Calcite, followed by Dolomite, Clay, Amphibole
etc., Feldspar, and Quartz. Among them, Calcite and Dolomite showed distinctly higher efficiency in collecting sulfate than
the other types.
A positive correlation was found with the number of S containing particles and the relative humidity. Calcite in particular,
since almost all of its particles was found to contain S above 60% r.h. On the other hand, the active uptake of SO2 by the carbonates was not suggested in the free troposphere downwind, and all the mineral classes exhibited similar S content.
Relative humidity in the free troposphere was suggested as the key factor controlling the SO2 uptake among the mineral types. In terms of sulfate loadings, the relationship was not linear, but rather increased exponentially
as a function of relative humidity. The humidity-dependent uptake capacity of mineral types altogether showed an intermediate
value of 0.07 gSO4
2− g−1 mineral at 30% r.h. and 0.40 gSO4
2− g−1 mineral at 80%, which is fairly consistent with laboratory experiments. 相似文献
12.
Bohan Liao Zhaohui Guo Qingru Zeng Anne Probst Jean-Luc Probst 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):151-161
Leaching experiments of rebuilt soil columns with two simulated acid rain solutions (pH 4.6–3.8) were conducted for two natural
soils and two artificial contaminated soils from Hunan, south-central China, to study effects of acid rain on competitive
releases of soil Cd, Cu, and Zn. Distilled water was used in comparison. The results showed that the total releases were Zn>Cu>Cd
for the natural soils and Cd>Zn≫Cu for the contaminated soils, which reflected sensitivity of these metals to acid rain. Leached
with different acid rain, about 26–76% of external Cd and 11–68% external Zn were released, but more than 99% of external
Cu was adsorbed by the soils, and therefore Cu had a different sorption and desorption pattern from Cd and Zn. Metal releases
were obviously correlated with releases of TOC in the leachates, which could be described as an exponential equation. Compared
with the natural soils, acid rain not only led to changes in total metal contents, but also in metal fraction distributions
in the contaminated soils. More acidified soils had a lower sorption capacity to metals, mostly related to soil properties
such as pH, organic matter, soil particles, adsorbed SO4
2−, exchangeable Al3+ and H+, and contents of Fe2O3 and Al2O3. 相似文献
13.
Characterization of Atrazine-Loaded Biodegradable Poly(Hydroxybutyrate-Co-Hydroxyvalerate) Microspheres 总被引:2,自引:0,他引:2
Renato Grillo Nathalie F. S. de Melo Renata de Lima Roberto Wagner Lourenço André Henrique Rosa Leonardo Fernandes Fraceto 《Journal of Polymers and the Environment》2010,18(1):26-32
Polyhydroxybutyrate-co-hydroxyvalerate microspheres (PHBV-MS) were prepared as a delivery system for the herbicide atrazine
(ATZ). Characterization of the system included investigation of in vitro release properties and genotoxicity. ATZ − PHBV-MS
particle diameters showed a size distribution range of 1–13 μm. Differential scanning calorimetry analyses indicated that
ATZ was associated with the PHBV microparticles. The release profiles showed a different release behavior for the pure herbicide
in solution, as compared with that containing ATZ-loaded PHBV-MS. Korsmeyer–Peppas model analyses showed that atrazine release
from the microparticles occurred by a combination of diffusion through the matrix and partial diffusion through water-filled
pores of the PHBV microparticles. A Lactuca sativa test result showed that the genotoxicity of ATZ-loaded PHBV-MP was decreased in relation to ATZ alone. The results demonstrate
a viable biodegradable herbicide release system using atrazine for agrochemical purposes. 相似文献
14.
Masaru Watanabe Shuhei Sawamoto Tadafumi Adschiri Kunio Arai 《Journal of Material Cycles and Waste Management》2001,3(2):99-102
This paper gives the results of partial oxidation experiments of polyethylene (PE) in supercritical water (SCW). The experiments
were carried out at a reaction temperature of 693K and a reaction time of 30 min using 6 cm3 of a batch-type reactor. The loaded sample weight was 0.3 g and there was 2.52 g water (0.42 g/cm3). The ratio of oxygen atoms to carbon atoms was 0.3. The results show a significant CO formation in O2–SCW, and the 1-alkene/n-alkane ratio in partial oxidation was higher than that in SCW pyrolysis. These results suggest the possibility of the hydrogenation
of hydrocarbon through partial oxidation followed by a water–gas shift reaction.
Received: July 19, 2000 / Accepted: September 28, 2000 相似文献
15.
High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA–CA, and PMMA–CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA–CA and PMMA–CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP. 相似文献
16.
Field trials with inorganic fertilizer (nitrogen, phosphorus, and potassium) nutrients were simulated in the greenhouse to remediate hydrocarbon‐polluted soils from a spill site in the Niger Delta, Nigeria. Samples of the polluted soils taken from two depths were displayed in a randomized complete block (RCB) design and treated with 10–100 g of (NH4)2SO4, KH2PO4, and KCl. The agronomic addition of the chemical nutrients was found to enhance the concentrations of nitrate‐nitrogen, phosphate‐phosphorus, and potassium in the soils. Pretreated nitrate‐nitrogen content ranged from 432 to 590 mg/kg in the polluted samples (with a control at 522 mg/kg), while posttreatment concentrations were 3,285 ± 154 mg/kg and 3,254 ± 159 mg/kg for surface and subsurface soils, respectively. © 2007 Wiley Periodicals, Inc. 相似文献
17.
Zhe Liu Hao Wei Jie Bai Jing Zhang Dongyan Liu Sumei Liu 《Water, Air, & Soil Pollution: Focus》2007,7(6):607-623
A 3-D biological model was developed and coupled to a hydrodynamic model, i.e., Princeton Ocean Model, to simulate the seasonal
variation and budget of dissolved inorganic nitrogen, phosphate, and silicate in Jiaozhou Bay. The modeled nutrients distribution
pattern is consistent with observation. Silicate, the most important limiting element for phytoplankton growth, is characterized
by consumption in spring, increase in summer and autumn, and accumulation in winter, whereas dissolved inorganic nitrogen
and phosphorous have increasing trend with low rates in spring, due to excessive river loads. Phytoplankton plays an important
role in nutrient renewal by photosynthesis and respiration processes. During an annual cycle, 7.83 × 103 t N, 0.28 × 103 t P, and 3.93 × 103 t Si are transported to the bay’s outer sea, i.e., the Yellow Sea, suggesting that Jiaozhou Bay is a significant source of
nutrients for the Yellow Sea. The spatial distribution of nutrients is characterized by vertically homogeneous profiles, with
high concentration inside the bay and low concentration toward the bay channel. These features are mainly governed by strong
turbulent mixing, fluvial influx, water exchange rate, and Yellow Sea water intrusion. Numerical experiments suggest that
the government should pay enough attention to proper layout of sewage drainage. 相似文献
18.
Mary Beth Adams James N. Kochenderfer Pamela J. Edwards 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):267-273
In 1989, a watershed acidification experiment was begun on the Fernow Experimental Forest in West Virginia, USA. Ammonium
sulfate fertilizer (35.5 kg N ha−1 yr−1and 40.5 kg S ha−1 yr−1) was applied to a forested watershed (WS3) that supported a 20-year-old stand of eastern deciduous hardwoods. Additions of
N and S are approximately twice the ambient deposition of nitrogen and sulfur in the adjacent mature forested watershed (WS4),
that serves as the reference watershed for this study. Acidification of stream water and soil solution was documented, although
the response was delayed, and acidification processes appeared to be driven by nitrate rather than sulfate. As a result of
the acidification treatment, nitrate solution concentrations increased below all soil layers, whereas sulfate was retained
by all soil layers after only a few years of the fertilization treatments, perhaps due to adsorption induced from decreasing
sulfate deposition. Based on soil solution monitoring, depletion of calcium and magnesium was observed, first from the upper
soil horizons and later from the lower soil horizons. Increased base cation concentrations in stream water also were documented
and linked closely with high solution levels of nitrate. Significant changes in soil chemical properties were not detected
after 12 years of treatment, however. 相似文献
19.
Nutrient and N2O concentrations in the water columns were measured seasonally over a full salinity range in the nutrified rivers Colne, Stour, Orwell, Deben, Trent, Ouse and Humber and their estuaries on the east coast of England between August 2001 and May 2002, and in the oligotrophic rivers Conwy, Dovey and Mawddach in North and West Wales between August 2002 and May 2003. Nutrient and N2O concentrations in the nutrified English rivers and estuaries were much higher than those in the Welsh rivers. N2O concentrations and % saturation in the estuaries were significantly correlated with nitrate, nitrite and ammonium concentrations in the water. The strongest correlation was with nitrite (r2 = 0.56, p < 0.01), suggesting that nitrite was the most significant factor among the different nutrients in regulating N2O concentration in the estuaries. N2O concentrations in the English rivers and estuaries were supersaturated throughout the year with annual averages from 186.9 to 992.9%, indicating that these rivers and estuaries were sources of atmospheric N2O, whereas in the Welsh rivers N2O concentrations were much lower with annual averages from 113.6 to 137.4% saturation. Although the estuarine area in the Colne was almost the same as that in the Conwy, the annual N2O emission from the Colne was much higher (937498 mol N yr–1) than in the Conwy (23020 mol N yr–1). On the east coast, riverine emissions of N2O were only 0.5–12.5% of the total emission from rivers and estuaries. Thus rivers were negligible, but estuaries were significant contributors to the UK N2O inventory. 相似文献
20.
Nutrient and N2O concentrations in the water columns were measured seasonally over a full salinity range in the nutrified rivers Colne, Stour, Orwell, Deben, Trent, Ouse and Humber and their estuaries on the east coast of England between August 2001 and May 2002, and in the oligotrophic rivers Conwy, Dovey and Mawddach in North and West Wales between August 2002 and May 2003. Nutrient and N2O concentrations in the nutrified English rivers and estuaries were much higher than those in the Welsh rivers. N2O concentrations and % saturation in the estuaries were significantly correlated with nitrate, nitrite and ammonium concentrations in the water. The strongest correlation was with nitrite (r 2 = 0.56, p < 0.01), suggesting that nitrite was the most significant factor among the different nutrients in regulating N2O concentration in the estuaries. N2O concentrations in the English rivers and estuaries were supersaturated throughout the year with annual averages from 186.9 to 992.9%, indicating that these rivers and estuaries were sources of atmospheric N2O, whereas in the Welsh rivers N2O concentrations were much lower with annual averages from 113.6 to 137.4% saturation. Although the estuarine area in the Colne was almost the same as that in the Conwy, the annual N2O emission from the Colne was much higher (937498 mol N yr?1) than in the Conwy (23020 mol N yr?1). On the east coast, riverine emissions of N2O were only 0.5–12.5% of the total emission from rivers and estuaries. Thus rivers were negligible, but estuaries were significant contributors to the UK N2O inventory. 相似文献